The present invention relates to a giant-magneto-resistive (GMR) or tunnel-magnetoresistive (TMR) magnetic head used in a hard disk drive.
In recent years, a dramatic improvement in the areal density of a hard disc drive has been desired, and for achieving this improvement, it is necessary to greatly reduce the flying height of a magnetic head relative to a magnetic recording medium from present levels of about 30 nm. To realize this reduction of the flying height, it is essential to work with higher accuracy the slider surface (air bearing surface) of the magnetic head disposed opposite to the rotating magnetic recording medium.
In general, magnetic heads have been fabricated as follows. On a hard substrate of Al2O3xe2x80x94TiC (alumina titanium carbide), etc. are formed a base coat of Al2O3 (alumina, film thickness of 2-10 xcexcm), an element (GMR element or TMR element) comprising a shield layer, a gap film and a magneto-resistive film etc. and an overcoat (alumina layer), all of which are sequentially laminated. The above structure is formed on a substrate having a size of 5 inches by a thin-film process in which lithography is used. After that, this substrate is cut by use of a diamond blade (diamond wheel) to row bars each having a length of 2 inches. After removing strains caused during the cutting by a method such as two-face lapping etc., the slider surface (air-bearing surface) of the magnetic head opposed to the magnetic recording medium is formed by the high-accuracy lapping of a surface of the structure directed at right angles to the layers thereof laminated on the substrate. After that, by cutting each of the row bars into small pieces containing individual magnetoresistive elements, a magnetic head is completed.
In the above method of lapping the row bar, the row bar bonded to a lapping jig is made to slide under pressure on a rotating lapping plate made of a metal while dripping onto the lapping plate a slurry containing abrasive grains of diamond etc. As lapping conditions, there are a case where the lapping jig on which the row bar is stuck is rotated on its axis and around the rotating lapping plate, and another case where the row bar is made to oscillate in a direction intersecting at right angles to the direction of rotation of the lapping plate, etc.
However, because the mechanical hardness of each of the portions that constitute the row bar, i.e., the substrate, the base coat, the magnetic element, the overcoat, etc. is different from each other, it is very difficult to uniformly lap them when using the above prior art. Therefore, in a completed magnetic head, a large recession is formed between the air-bearing surface of the substrate and the magnetic element, which recession causes a substantial increase in the flying height, so that there occurred such an inconvenience as it is difficult to efficiently reproduce information from a large-capacity magnetic recording medium.
Further, among the portions that constitute the row bar, the magnetic element has a lower mechanical hardness and is most susceptible to the adverse effect of abrasive grains used. In other words, the magnetic element has a layered structure having a lower shield layer, a magnetoresistive film, and an upper shield layer etc. and the film thickness of this magnetoresistive film is very thin (for example, several tens of nano-meter) and, therefore, scratches traversing the magnetoresistive film from the above shield layers are apt to be formed.
In a case where the depth of this scratch is large, an electrical short path is formed between the upper and lower shield layers including the magnetoresistive film, and this electrical short path not only causes the function of the magnetoresistive element portion to be lost, but also forms a dead layer during the lapping, so that the characteristics of the magnetic head itself and the reliability thereof are greatly influenced. For this reason, further planarization of a lapped surface is also required simultaneously.
The object of the invention is to solve the above problems and to obtain a magnetic head used for reading or writing magnetic recording information in which magnetic head the pole tip recession occurring between the substrate and the magnetic element is minimized and in which magnetic head the smoothness of a lapped surface is improved.
According to the first aspect of the invention achieving the object, there is provided a magnetic head comprising a substrate, a base coat located on the substrate and a magnetic element located on the base coat, the film thickness of the base coat being in a range of 0.05 to 0.5 xcexcm.
According to the second aspect of the invention, a distance defined between an air-bearing surface provided on a substrate surface, which surface intersects at right angles a face along which the magnetic element is located, and a terminal face of the magnetic element which terminal face is located on the same side as the air-bearing surface is in a range not more than 1 nm and, at the same time, an average surface roughness of this air-bearing surface is in another range not more than 10 nm.
According to the third aspect of the invention, the Vickers hardness of the base coat is lower than that of the substrate and is higher than that of the magnetic element, and the film thickness of the base coat is in a range of 0.05 to 0.5 xcexcm. Specifically, the base coat is formed of Al2O3 (alumina) and the substrate is formed of Al2O3xe2x80x94TiC (alumina titanium carbide).
In the present invention, it becomes possible to realize a magnetic head in which a recession occurring between the substrate and the magnetic element is minimized and in which the smoothness of a lapped surface is remarkably improved.